Background: Multiple sclerosis (MS) is one of the most common autoimmune diseases in adults that cause disability in patients. Different studies were conducted on more rapid diagnosis of the disease such as measuring serum or cerebrospinal fluid (CSF) contents.Objectives: The current study aimed at measuring amyloid β (Aβ) serum levels in patients with relapsing-remitting MS.Materials and Methods: In the current case-control study, the serum levels of Aβ were measured in 48 patients with RRMS and 33 healthy controls using the enzyme-linked immunosorbent assay (ELISA) technique in Isfahan, Iran, from 2014 to 2016. Data analysis was conducted with SPSS.Results: The mean serum level of Aβ in the case (patients with RRMS) and control groups were 192.75±125.65 and 128.11±85.20 pg/mL, respectively; so serum Aβ levels in the RRMS group was significantly higher than healthy controls (p=0.02). Also, there was a positive significant correlation between the serum Aβ levels and the expanded disability status scale (EDSS) (r=+0.85, p<0.0001).Conclusions: Owing to the increase of serum Aβ level in patients with RRMS and its significant increase in severe MS cases (higher EDSS scores), so serum Aβ level can be considered as a marker for MS and its progression.